Key words BTEX • Benzene • Toluene • Ethyl-Benzene • Xylene VOCs • Air quality • Indoor pollution • Gasoline emission

Volatile organic compounds (VOCs) are released con-tinuously into the indoor environment from a number of sources including building materials, furnishings and household products like air fresheners. In addition there are many activities carried out in houses that release VOCs intermittently. However, a major contrib-utor to indoor pollution, particularly in large cities, is the outdoor environment largely through the concen-tration of vehicular traffic. In the present study, con-ducted in Tehran, the group of gasoline components commonly known as BTEX were measured as a surro-gate for this pollution under different conditions in the indoor environment. Using a method published by NIOSH, organic vapours were collected by drawing air through charcoal-filled tubes with a portable pump with a flow rate of 0.2m3.min1. Organic material from the collected samples was eluted from the charcoal tubes by carbon disulphide and the BTEX component analysed by Gas Chromatography. The results showed that proportionally high levels of BTEX were present in the VOC profile and it was concluded that petroleum and its combustion products were major contributors to indoor pollution in Tehran. Also, the concentration of benzene was especially high, being some 2–4 times greater than the maximum levels recommended by many countries